When production from a hydrocarbon well attainable through natural means (e.g., pressure within the wellbore) is no longer sufficient for the well to remain economically viable, numerous types of secondary recovery methods exist to increase the productivity of the well. One such method includes use of a downhole pump that is inserted into the wellbore, then actuated to draw hydrocarbons and/or other fluids toward the surface. Conventionally, downhole pumps are actuated by physically manipulating values and/or other operable parts from the surface, through movement of a pump jack or similar powered device, that is connected to the downhole pump using a long string of joined connectors, termed “sucker rods.”
Conventional sucker rod strings are formed from lengths of steel rod, having threaded connectors at each end for engaging adjacent segments of rod, to form a string of sufficient length to connect a pump jack to a down hole pump. Because steel is heavy, expensive, and suffers from other inherent difficulties, alternative types of sucker rod materials have been explored, such as fiberglass. Fiberglass offers an equivalent or greater tensile strength than steel, while being both lighter and less costly, enabling a string of fiberglass sucker rods to be reciprocated using less energy and smaller equipment. Fiberglass rods also possess the ability to stretch in an axial direction, such that each stroke of a pump jack can be assisted by the natural expansion and contraction of the sucker rod string, allowing for shorter and more energy efficient strokes.
The ends of fiberglass rod segments used in a sucker rod string can be connected by use of threaded end connectors or end fittings, typically made from steel. An epoxy or other suitable resin can be introduced into the end fitting for bonding to and between the exterior of the fiberglass rod segment and interior of the end fitting. By providing epoxy or other resin into the interior of an end fitting, the epoxy or other resin when cured bonds to the fiberglass rod segment, while filling the interior cavity of the end fitting. The cured epoxy or other resin (“resin material”) prevents removal or displacement of the rod from the end fitting during use.